Electrical cable insulation slitting tool



3,279,058 ELECTRICAL CABLE INSULATION SLITTING TOOL Filed April 14, 1965 C. E. DIBBLE Oct. 18, 1966 2 Sheets-Sheet 1 INVENTOR. CHARLES E. D/8BLE BY 7w-i c. E. DIBBLE 3,279,058 ELECTRICAL CABLE INSULATION SLITTING TOOL Filed April 14. 1965 2 Sheets-Sheet 2 Oct. 18, 1966 5, kfim OB e w m I l l ll United States Patent 3,279,058 ELECTRICAL CABLE INSULATION SLITTING TOOL Charles E. Dibble, West Redding, Conn., assignor to Burndy Corporation, a corporation of New York Filed Apr. 14, 1965, Ser. No. 448,085 2 Claims. (Cl. 30-903) This invention pertains to cable insulation cutters, and particularly to cutters for longitudinally slitting the relatively thick insulation commonly used on heavy duty electric power cables.

Many types of heavy duty electric power cables, such as those commonly used to supply power to portable mine machinery, for example, are characterized by thick coverings of tough, cut-and-abrasion-resistant, insulating materials. When it becomes necessary to remove this insulation for the purpose of making connections or repairs, however, these otherwise highly desirable characteristics are generally found to be quite undesirable from the standpoint of cutting and trimming operations. Toughness and cut resistant qualities substantially increase the efiort required to manually penetrate, cut away and remove this insulation in order to bare the underlying cable conductors.

Although a great variety of knife-edged hand tools are commercially available for cutting and removing cable insulation, these presently known devices are generally not particularly suited for heavy duty usage. Since they are commonly intended for relatively soft insulation, the operator is not afforded adequate mechanical advantage for readily penetrating the type of tougher insulation under discussion. Many of these devices further require the operator to supply simultaneously the force required to penetrate into the insulation and the force required to perform the cutting operation. Other tool-s which overcome some of these disadvantages through the use of pivot or hinge mounted cutting elements suflfer, on the other hand, from the disadvantage of relatively fragile and easily broken support arrangements for the cutting elements.

Accordingly, it is an object of this invention to provide a cutting tool for cable insulation wherein the elfort required to penetrate tough cable insulation is less than in prior tools used for the same purpose.

A further object is to provide a cutting tool which simply and effectively maintains a cutting blade in proper engagement with the insulation of an electric cable during cutting of the insulation.

A still further object is to provide a tool wherein the cutting blade may be securely mounted to a relatively rigid structural part of the tool but may nevertheless be readily removed for repair or replacement.

Features of this invention include the use of a housing member having a cable receiving channel therethrough which includes a movable wall portion adapted to force an inserted cable into cutting engagement with a cutting blade and to thereafter maintain the cable in cutting relationship with the cutting blade as the housing is moved axially along the cable.

These and other objects, features, and advantages of this invention are more clearly illustrated and particularly pointed out in the following specification and claims, and in the accompanying drawings, in which:

FIG. 1 represents a pictorial view of an embodiment of this invention having a movable wall portion in a cable receiving channel;

FIG. 2 is a front elevation View of the embodiment shown in FIG. 1;

FIG. 3 is a bottom plan view of the same embodiment;

FIG. 4 is a side section view of the cutting tool of FIG.

1, showing a cable and the tool parts in initial engagement position;

FIG. 5 is a side section view showing the cable and tool parts in final cutting position;

FIG. 6 is a transverse section view through a cable such as might be used in connection with this invention;

FIG. 7 is a pictorial representation of a disassembled mounting block such as might be used to support a cutting blade in a tool constructed in accordance with this invention.

Referring now more particularly to the drawings, the cutting tool illustrated in FIGS. 1 through 5 may be seen to comprise a housing member designated generally by reference numeral 10, which includes a pair of upright opposed side walls 12, 14 coupled together in generally U-shaped configuration by a connecting wall element 16. Movable wall element 18 and insert element 20 extend between the side wall 12, 14, in opposed spaced-apart relationship to define, in cooperation with the side walls, a longitudinal channel 22 extending through the housing 10. One or more cutting blades 24 are coupled to the housing 10 by means of insert 20 so as to project into the longitudinal channel 22 in position for penetrating the insulation of a cable telescopically disposed within the channel. Gripping handles such as 26 are provided on the housing 10 to facilitate drawing the blade or blades 24 longitudinally along and through the insulation of a cable constrained in channel 22.

The operation of this invention is best illustrated by FIGS. 4 and 5, wherein it may be seen that in the first, or retracted, position of wall member 18, a cable 30 may be inserted into the housing 10 at an angle to the axis of longitudinal channel 22 so as to substantially clear cutting blade 24. Subsequent to insertion of the cable, wall member 18 may be moved to a second, extended position, as shown in FIG. 5, wherein the cable 30 is forced into a position substantially parallel to the axis of channel 22 so that cutting blade 24 necessarily penetrates the cable insulation to a predetermined depth; this penetrated position will be maintained so long as wall member 18 remains in the location shown. The cable 30 is then free to move in the longitudinal direction only, as indicated by arrow B in FIG. 5, so that the sharpened cutting edge 27 of blade 24 will move axially along and through the cable insulation until a slit of the desired length has been formed.

The dimensions of blade 24 may be selected to correspond to a particular cable and particular channel dimension so as to form a slit in the insulation extending from the outer surface thereof through to the surface of the encased conductor. By removing a cable which has been slit, rotating it about its own axis, and reinserting it into this tool, a second slit may be formed which is coextensive in length and directly opposite the first; the insulation which has thus been slit on both sides of a cable may then bepeeled away in two separate halves to expose the underlying conductor.

FIG. 6 illustrates a transverse cross section of a heavy duty cable 30 which might be used in connection with this invention. The cable is seen to include a pair of round wire conductors 31, 33 and a central flat conductor 32 which are together encased in a common insulating jacket 34. Three parallel longitudinalslits 3'5, 36 and 37 have been formed in the jacket in the cable, extending from the outer surface of jacket 34 to the surf-ace of the conductors, in the manner described above. Dotted lines 35, 36 and 37' illustrate the-position of corresponding opposite slits which might be formed by use of the rotation and reinsertion process also described above.

Movable wall portion 18 is slidably coupled to the housing 10 by means of a stud fastener 28 which extends 3 through longitudinal slot 29 in wall portion 16. The slot and stud capture portion 18 to portion 16 while permitting longitudinal relative motion therebetween. Movable portion 18 is thus freely movable between a forward position, as shown in FIG. 4, in which cable 30 may be inserted through the housing 10 at an angle to the axis of channel 22, and a rearward position, as shown in FIG. 5, in which the cable 30 is constrained to telescopic movement substantially parallel to the axis of channel 22. It has been found that the frictional relationship between the commonly used cable insulating materials and the structural materials which may expectably be used for a housing such as 10, is such that wall member 18 will ordinarily be drawn from the forward position shown in FIG. 4 to the rearward position of FIG. 5 merely in response to movement of cable 30 in the rearward direction (direction of arrow B) relative to housing 10. The rearward movement of wall portion 18 will force cable 30 to tilt about the edge of the wall portion into alignment with the channel axis (as shown by the direction of arrow A in FIG. 4), gradually forcing penetration of the blade 24 into the cable and ultimately holding the cable in its final, penetrated position ready for slitting.

To provide adequate peripheral constraint for the cable during the cutting operation, the side walls 12 and 14 may be made to extend rearwardly so as to define, in effect, a longitudinal opening 17 which extends through the wall 16 of the housing 10 and through the rearward end of the housing. As seen in FIG. 4, the longitudinal opening 17 permits the desired insertion of the cable 30 at an angle to the axis of the channel 22. The rearward posi tion of slidable Wall portion 18 may thus be considered to cover over or to obstruct the longitudinal opening 17.

In the embodiment illustrated in FIGS. 1 through 5, cutting blades 24 have been shown to be embedded in insert element 20. FIG. 7 illustrate an alternative means of supporting a cutting blade in a hand tool constructed in accordance with this invention. In this configuration a pair of structural elements 50 and 52 are fitted with a cutout seat such as 54 on the interface of one or both of the elements which is adapted to receive and clamp a cutting blade such as the blade 56 between them. The blade 56 may be provided with tab portions such as 58 adapted to mate with corresponding portions of the cutout 54 to assure multidirectional tension of the blade within the cutout.

To retain element in proper position relative to the remainder of the housing member 10, a pair of transversely extending key portions 40 project from the sides of element 20 in position to mate with corresponding longitudinal keyways 42 formed in side walls 12 and 14. A pair of tabs or stop members 44 obstruct the rearward end of keyways 44 to limit the rearward movement of insert element 20. Rearward relative movement of an inserted cable 30 will thus serve to draw the blade or blades 24, and attached insert 20, more firmly against stop members 44.

Insert element 20 has further been shown to include a 5 pair of downwardly depending leg portions 46 which lie parallel to the opposed side walls 12 and 14. These leg portions serve to effectively delimit the dimensions of enclosed channel 22. It is apparent that various differently dimensioned insert members 20 may be used in conjunction with a given housing member 10 in order to accommodate a fairly wide range of different cable sizes. Insert 20 may, of course, be used without any depending leg portions in order to accommodate a cable of maximum width; maximum width in such case is determined by the spacing between the opposed side walls 12 and 14. Similarly, the housing member 10 may be formed within an integral top wall (not shown) in place of insert element 20, and the cutting blade or blades 24 may, in turn, be mounted to such an integral top wall. Still further, an integral top wall may be used in conjunction with an insert element such as 20. v

The invention has thus been described but it is desired to be understood that it'is not confined to the particular forms or usages shown and described, the same being merely illustrative, and that the invention may be carried out in other ways without departing from the spirit of the invention; therefore, the right is broadlyclaimed to employ all equivalent instrumentalities coming within the scope of the appendent claims, and by means of which objects of this invention are attained and new results accomplished, as it is obvious that the particular embodiments herein shown and described are only some of the many that can be employed to obtain these objects and accomplish these results.

I claim:

1. A hand tool for longitudinally slitting the insulating jacket surrounding the electrical conductor in a heavy duty electrical cable, comprising:

a housing member having an interior surface defining a longitudinal channel of given cross sectional shape, said channel extending through said housing member between a rearward and a forward end;

a longitudinal opening in said interior surface wall extending through at least the rearward end thereof;

a housing sub-portion slidably coupled to said housing for longitudinal movement between a forward position wherein a cable may be inserted into said channel at an angle to the longitudinal axis thereof, and a second position wherein a cable within said channel is constrained to telescopic motion substantially parallel to theaxis thereof;

an insulation cutting blade coupled to said housing member and projecting into said longitudinal channel, said cutting blade being located within said channel in position to clear a cable inserted into said channel at an angle to the axis thereof, and to penetrate into the insulation of such a cable as the axis of the cable is tilted into a position substantially parallel to the axis of the said longitudinal channel,

whereby longitudinal relative motion of said housing along a cable will move said cutting blade axially through the insulation of the cable at a given depth.

2. The hand tool of claim 1 further including insert means adapted to be substantially telescopically inserted into said longitudinal channel todelimit the cross section thereof; and retainer means for preventing over insertion of said insert means into said channel.

References Cited by the Examiner UNITED STATES PATENTS 2,347,956 5/ 1944 Lansing 30-91 2,686,362 8/1954 Dancey 30-92 2,735,175 2/ 1956 Talhnan 30-96 2,871,739 2/ 1959 Granzow 81-95 2,903,064 9/1959 Blonder 30-95 WILLIAM FELDMAN, Primary Examiner.

MY RON C. KRUSE, Examiner. 

1. A HAND TOOL FOR LONGITUDINALLY SLITTING THE INSULATING JACKET SURROUNDING THE ELECTRICAL CONDUCTOR IN A HEAVY DUTY ELECTRICAL CABLE, COMPRISING: A HOUSING MEMBER HAVING AN INTERIOR SURFACE DEFINING A LONGITUDINAL CHANNEL OF GIVEN CROSS SECTIONAL SHAPE, SAID CHANNEL EXTENDING THROUGH SAID HOUSING MEMBER BETWEEN A REARWARD AND A FORWARD END; A LONGITUDINAL OPENING IN SAID INTERIOR SURFACE WALL EXTENDING THROUGH AT LEAST THE REARWARD END THEREOF; A HOUSING SUB-PORTION SLIDABLY COUPLED TO SAID HOUSING FOR LONGITUDINAL MOVEMENT BETWEEN A FORWARD POSITION WHEREIN A CABLE MAY BE INSERTED INTO SAID CHANNEL AT AN ANGLE TO THE LONGITUDINAL AXIS THEREOF, AND A SECOND POSITION WHEREIN A CABLE WITHIN SAID CHANNEL IS CONSTRAINED TO TELESCOPIC MOTION SUBSTANTIALLY PARALLEL TO THE AXIS THEREOF; AN INSULATION CUTTING BLADE COUPLED TO SAID HOUSING MEMBER AND PROJECTION INTO SAID LONGITUDINAL CHANNEL, SAID CUTTING BLADE BEING LOCATED WITHIN SAID CHANNEL IN POSITION TO CLEAR A CABLE INSERTED INTO SAID CHANNEL AT AN ANGLE TO THE AXIS THEREOF, AND TO PENETRATE INTO THE INSULATION OF SUCH A CABLE AS THE AXIS OF THE CABLE IS TILTED INTO A POSITION SUBSTANTIALLY PARALLEL TO THE AXIS OF THE SAID LONGITUDINAL CHANNEL, WHEREBY LONGITUDINAL RELATIVE MOTION OF SAID HOUSING ALONG A CABLE WILL MOVE SAID CUTTING BLADE AXIALLY THROUGH THE INSULATION OF THE CABLE AT A GIVEN DEPTH. 